CN116368267A

CN116368267A - Method for producing an electroplated product by depositing a bottom layer, a diffusion barrier layer and a top layer on a substrate surface, and an electroplated product thus produced

Info

Publication number: CN116368267A
Application number: CN202180073859.3A
Authority: CN
Inventors: C·奈利斯; S·贝格里奥米尼
Original assignee: Coventya SpA
Current assignee: Coventya SpA
Priority date: 2020-11-16
Filing date: 2021-11-15
Publication date: 2023-06-30
Also published as: EP4001472A1; EP4244409A1; WO2022101474A1

Abstract

The invention relates to a method for producing an electroplated product by depositing a bottom layer, a barrier diffusion layer and a top layer on a surface of a substrate comprising or consisting of a copper or copper layer or copper alloy layer, wherein the bottom layer comprises or consists of a noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof and the top layer comprises or consists of a noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof. The bottom layer and the top layer are separated by a barrier diffusion layer comprising or consisting of indium or an indium alloy. The barrier layer prevents interdiffusion between the bottom layer and the top layer. Furthermore, the invention relates to an electroplated product obtainable by such a method.

Description

Method for producing an electroplated product by depositing a bottom layer, a diffusion barrier layer and a top layer on a substrate surface, and an electroplated product thus produced

In the field of electroplating of decorative articles such as custom jewelry, a common electroplating sequence involves depositing an acidic copper underlayer on the surface of a substrate to ensure proper leveling of the substrate roughness, followed by a white bronze layer of 2 μm to 5 μm and a thin palladium-based layer of 0.2 μm to 0.5 μm thickness to prevent diffusion of the top noble metal layer, principally gold or gold alloy, into the copper or copper alloy underlayer, and most importantly to prevent copper diffusion into the noble metal layer.

This type of sequence is now preferred as a substitute for the nickel underlayer, since nickel has been prohibited from being used in articles that are in direct and long-term contact with human skin according to the REACH instruction. An alternative is a palladium layer. However, the use of palladium is problematic because of its significant price increase due to its widespread use in other applications.

The bronze technique of the present invention primarily uses cyanide as a complexing agent to effect co-deposition of a ternary alloy of copper, tin and zinc, which is also effective as a copper diffusion barrier.

Deposition of indium on copper can lead to two different problems based on the thickness of the deposit. If the deposit has a low thickness, the operator may be caused to doubt the presence of the deposit on the surface due to the "translucent" aspect of the operator. Higher thicknesses can lead to many defects on the deposit until an unacceptable matt deposit is obtained for aesthetic reasons.

EP 3 ° 540 ° 097 ° A1 discloses an electroplated product having a combination of layers for providing a diffusion barrier layer below a noble metal top layer on a substrate comprising a copper-based material and/or a copper-based underlayer, such that the layer or combination of layers prevents or impedes migration of copper into the noble metal layer or into the opposite side. The diffusion barrier layer comprises indium or an indium alloy.

EP 2 ° 139 ° 012 ° A1 discloses a silver coated material for a movable contact component comprising a conductive base member composed of copper or a copper alloy; a primer layer composed of nickel or a nickel alloy to be coated on the conductive base member; an intermediate layer composed of palladium, or a palladium alloy, or a silver-tin alloy to coat on the underlayer; and an outermost surface layer composed of silver or silver alloy and formed on the intermediate layer.

US 2013/0224515 A1 discloses a thin indium metal layer which is electroplated onto the silver to prevent the silver from tarnishing. The composite of indium and silver has high conductivity.

EP 3 ° 359 ° 710 ° A1 discloses a method for depositing indium or indium alloy and an article obtained by the method, wherein the method comprises the steps of:

i. providing a substrate having at least one metal surface or metal alloy surface;

depositing a first indium or indium alloy layer on at least a portion of the surface, thereby forming a combined phase layer from a portion of the metal or metal alloy surface and a portion of the first indium or indium alloy layer;

partially or completely removing the portion of the first indium or indium alloy layer that has not been formed into the combined phase layer;

depositing a second indium or indium alloy layer on at least a portion of the surface obtained in step iii.

None of those prior art documents discloses a diffusion barrier comprising indium between two layers comprising noble metals. Those prior art disclosing indium barriers are silent and the combination of achieving a high thickness of the barrier with good brightness necessary for products in the noble metal field is often complex.

It is therefore an object of the present invention to provide an electroplated product which has improved aesthetic stability by avoiding or substantially reducing copper diffusion into the noble metal top layer.

This problem is solved by a method for producing an electroplated product having the features of claim 1 and an electroplated product having the features of claim 9. Further dependent claims mention preferred embodiments.

According to the present invention, a method for preparing an electroplated product by electroplating a substrate comprises the steps of:

a) Depositing a bottom layer comprising or consisting of a first noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof from a first electrolyte on a surface comprising or having a copper coating, said first electrolyte comprising at least one source of corresponding noble metal ions and at least one conductive salt,

b) Depositing a diffusion barrier layer on the bottom layer using an aqueous electroplating bath comprising at least one source of indium ions and at least one conductive salt, wherein the diffusion barrier layer prevents interdiffusion between the substrate and the top layer,

c) A top layer comprising or consisting of a second noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof is deposited on the diffusion barrier layer with a second electrolyte comprising at least one source of corresponding noble metal ions and at least one conductive salt.

Surprisingly, it has been found that plating indium on noble metals results in a bright, transparent and white deposit. It has also been found that the underlayer allows for an increase in the thickness of the indium barrier layer while maintaining brightness. Furthermore, the bath can be handled more easily due to the fact that the plating bath is less sensitive to parameter variations. It was found that by using a noble metal underlayer under an indium diffusion barrier layer, the barrier properties of the indium diffusion layer can be significantly improved.

In a preferred embodiment, the aqueous electroplating bath of step b) has a pH in the range of 1 to 14, preferably 2 to 11, still more preferably 4 to 10.

In a preferred embodiment, in the aqueous electroplating bath of step b), the at least one source of indium ions is selected from the group consisting of indium sulfate, indium chloride, indium acetate, indium sulfamate, and combinations or mixtures thereof.

Hereinafter, all concentrations are mass concentrations, which refer to the mass of components in 1L of the aqueous plating bath.

In a preferred embodiment, the concentration of the at least one source of indium ions of the aqueous electroplating bath of step b) is from 0.1g/L to 20g/L, preferably from 0.2g/L to 15g/L, more preferably from 0.3g/L to 10g/L, and even more preferably from 0.5g/L to 10g/L.

In a more preferred embodiment, the aqueous electroplating bath of step b) contains a conductive salt to distribute the indium throughout the desired current density range. The conductive salt is selected and balanced to act not only as a conductive salt but also as a buffer. The conductive salt/buffer is preferably selected from the group consisting of citrates (e.g., sodium citrate or potassium citrate or their corresponding acidic forms), formates (e.g., sodium formate or their corresponding acidic forms), pyrophosphates (e.g., tetrapotassium pyrophosphate) and gluconates (e.g., sodium gluconate or potassium gluconate), nitrates, carbonates, borates, and combinations or mixtures thereof.

Preferably the aqueous electroplating bath of step b) comprises 30g/L to 600g/L, more preferably 40g/L to 500g/L, and most preferably 100g/L to 400g/L of at least one conductive salt. The concentration in this range is suitable for keeping the pH of the plating solution of the invention constant for multiple revolutions (TO) of the plating solution.

The brightness of the indium deposit is preferably controlled by adding a surfactant to the aqueous electroplating bath of step b). The surfactant acts as a wetting agent and reduces the surface tension to allow indium deposition. The surfactant may belong to the amphoteric family and is selected from propionic acid amino acids, propionic acid imino acids, quaternary alkyl betaines or sulfobetaines. The surfactant is preferably selected from betaine, aminobetaine, imidazoline, cocoamidopropyl betaine, N-dimethyl-N- (3-cocoamidopropyl) -N- (2-hydroxy-3-sulfopropyl) betaine ammonium, N-dimethyl-N-octadecyl-N- (3-sulfopropyl) betaine ammonium, N-dimethyl-N-dodecyl-N- (3-sulfopropyl) betaine ammonium, and combinations or mixtures thereof.

The aqueous electroplating bath in step b) preferably comprises from 0.01g/L to 5g/L, more preferably from 0.01g/L to 1.5g/L of surfactant.

To increase the solubility or to improve the electrodeposition in step b), the indium ions may be complexed in solution by complexing agents. The complexing agent is preferably selected from the group consisting of carbohydrates, amino acids, imino acids, sulfur compounds, sugar alcohols, and combinations or mixtures thereof. More preferably, the complexing agent is selected from the group consisting of sorbitol, mannitol, gluconate, erythritol, xylitol, nitrilotriacetic acid, cysteine, iminodiacetic acid, triethanolamine, and combinations or mixtures thereof. The complexing agent was found to be well suited for complexing indium ions.

The aqueous electroplating bath of step b) preferably comprises 0.5g/L to 100g/L, preferably 1g/L to 75g/L, most preferably 2.5g/L to 50g/L, and in particular 5g/L to 35g/L complexing agent. The concentrations within these ranges are sufficient to complex the indium ions contained in the electroplating solutions of the present invention. Complexing agent concentrations below 0.5g/L were found to be detrimental and unable to stabilize the bath at the desired pH.

Importantly, it has surprisingly been found that aqueous electroplating baths with non-complexed indium show a lack of stability at pH values above 2 and that the use of suitable complexing agents significantly improves the stability.

In a preferred embodiment, the sequence of steps a) to c) is not interrupted by any further deposition steps, with the result that the layers electroplated in steps a) to c) adjoin one another.

In a more preferred embodiment, the layers electroplated in steps a) to c) are directly adjacent to each other.

In a preferred embodiment, the source of at least one noble metal ion in the electroplating bath of step a) is at least one source of Au ions and/or Ag ions.

In a preferred embodiment, the at least one noble metal ion source in the electroplating bath of step c) is selected from at least one source of Au, ag, pd, pt ions or a combination thereof, preferably at least one source of Au ions and/or Ag ions.

In a preferred embodiment, in a further step d) immediately following the deposition step c), a passivation layer or a lacquer layer or a finish layer is deposited on the top layer.

In a more preferred embodiment, step d) comprises immersing the product obtained in step c) in a chemical solution.

Further, an electroplated product is provided comprising a substrate comprising copper or having a copper coating, on which a bottom layer comprising or consisting of a noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof and a top layer comprising or consisting of a noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof are deposited. The bottom layer and the top layer are separated by a diffusion barrier layer comprising or consisting of indium or an alloy of indium and the top layer material, which diffusion barrier layer prevents interdiffusion between the bottom layer and the top layer.

In a preferred embodiment, the underlayer has a thickness of 10nm to 500nm, preferably 25nm to 400nm, still more preferably 40nm to 300 nm.

In a preferred embodiment, the diffusion barrier layer has a thickness of 1nm to 500nm, preferably 25nm to 300nm, still more preferably 50nm to 250 nm.

In a preferred embodiment, the top layer has a thickness of 1nm to 500nm, preferably 3nm to 400nm, still more preferably 5nm to 300 nm.

In a preferred embodiment, the top layer consists of a noble metal selected from Au, ag, pd, pt and alloys thereof, preferably from Au, ag and alloys thereof.

In a more preferred embodiment, the first layer consists of gold or gold alloy.

In a preferred embodiment, a passivation layer or a paint layer or a finish layer is present on the top layer.

The subject matter according to the present invention is intended to be explained in more detail with reference to the following figures and examples, without wishing to limit the subject matter to the specific embodiments shown herein.

Fig. 1 shows the GDOES spectrum of example 1 without heat treatment (left side) and with heat treatment (right side).

Fig. 2 shows the GDOES spectrum of example 2 without heat treatment (left side) and with heat treatment (right side).

Fig. 3 shows the GDOES spectrum of example 3 without heat treatment (left side) and with heat treatment (right side).

Fig. 4 shows the GDOES spectrum of example 4 without heat treatment (left side) and with heat treatment (right side).

Fig. 5 shows the GDOES spectrum of example 5 without heat treatment (left side) and with heat treatment (right side).

Fig. 6 shows the GDOES spectrum of example 6 without heat treatment (left side) and with heat treatment (right side).

Fig. 7 shows the GDOES spectrum of example 7 without heat treatment (left side) and with heat treatment (right side).

Fig. 8 shows the GDOES spectrum of example 8 without heat treatment (left side) and with heat treatment (right side).

Fig. 9 shows the GDOES spectrum of example 9 without heat treatment (left side) and with heat treatment (right side).

Fig. 10 shows the GDOES spectrum of example 10 without heat treatment (left side) and with heat treatment (right side).

Fig. 11 shows the GDOES spectrum of example 11 without heat treatment (left side) and with heat treatment (right side).

Fig. 12 shows the GDOES spectrum of example 12 without heat treatment (left side) and with heat treatment (right side).

Examples

At the surface 0.22dm ² 5 experiments were performed on flat brass articles. The flat brass article was subjected to the following preparation sequence:

alkaline cathode cleaner (PRESOL 1540-4V-room temperature-110 seconds)

Acid activation (H2 SO4 2% -room temperature-1 min)

CIE laboratory measurements were performed using a Minolta CM-503i spectrophotometer. The illuminator used was Dayleght D65 (6500K) comprising a reflective component (sci). The observer was set to standard (10 °) and measurements were made in the color space CIE lxa x b x.

GDOES values were measured on GD-Profiler 2 from Horiba using software QUANTUM V2.08. The pressure was set at 650Pa, the power was set at 35W, no pulse, the module voltage was set at 6V, and the phase voltage was set at 5V.

Electroplating with gold：

Copper plating bath preparation

-COVENTYA process CUBRAC 440

-20℃–3A/dm ²

Deposition time: 15 minutes to reach 15 μm

Indium plating bath preparation (preparation A)

Sodium gluconate 100g/L

Sodium formate 100g/L

In 2g/L (from indium sulphate 100 g/L); pre-complexing with sorbitol (molar ratio of indium: sorbitol=1:4)

Operating conditions：

Temperature 25 ℃, current density: 1A/dm2, pH 10, time: 4 minutes

Indium plating bath preparation (preparation B)

-sodium formate 250g/L

100g/L citric acid

In 4g/L (from indium sulphate solution 100 g/L)

15ppm of cocoamidopropyl betaine

Operating conditions：

Temperature 50 ℃, current density: 2A/dm2, time: 2 minutes, pH 4.5

Jin Duyu formulations

-COVENTYA process AURANE 793

-40℃–2A/dm ²

Deposition time: 3 minutes to reach 0.5 μm

For our purposes, aesthetic aspects are not the only requirements. It must be verified that indium also functions as a copper migration barrier in this order.

To investigate this property, a number of panel pairs with different sequences were prepared. For each pair, one panel was placed in an oven at 180 ℃ for 24 hours to perform heat treatment. After subsequent aesthetic evaluation, GDOES analysis was performed on each panel to investigate the relative position of each metal making up each sequence.

In table 1 below, the GDOES analysis plots and color coordinates (in terms of measureable) of the samples are shown.

Examples 5 and 6 were prepared according to the invention, examples 1, 2, 3 and 4 were prepared as references or for comparative reasons.

Table 1 example with gold

The panel of example 1 was very dark and irregular in appearance after heat treatment. Fig. 1 demonstrates that after heat treatment, copper diffuses in gold to the surface.

In fig. 3, a blocking effect can be observed, but for the obtained panel, it is clear that the brightness of the gold layer is not optimal.

In fig. 4, specific behavior can be observed. After heat treatment, gold diffuses into the indium to the top, as can be seen from the color coordinates, and copper remains blocked. This demonstrates the affinity between gold and indium, and the barrier to copper migration is an indium-gold alloy.

In fig. 5, the two diagrams show very small differences, and color coordinates are also observed. GDOES analysis confirmed the properties of indium as a copper diffusion barrier in this new sequence.

From fig. 6, it was confirmed that the thickness of the gold underlayer did not affect the characteristics of the copper diffusion barrier of indium. The results were the same as in example 5.

Electroplating with silver：

Copper plating bath preparation

-COVENTYA process CUBRAC 440

-20℃–3A/dm ²

Deposition time: 15 minutes to reach 15 μm

Indium plating bath preparation (preparation A)

Sodium gluconate 100g/L

Sodium formate 100g/L

Operating conditions：

Temperature 25 ℃, current density: 1A/dm2, pH 10, time: 4 minutes

Indium plating bath preparation (preparation B)

-sodium formate 250g/L

100g/L citric acid

In 4g/L (from indium sulphate solution 100 g/L)

15ppm of cocoamidopropyl betaine

Operating conditions：

T50 ℃, current density: 2A/dm2, time: 2 minutes, pH 4.5

Jin Duyu formulations

-COVENTYA process AURANE 793

-40℃–2A/dm ²

Deposition time: 2 minutes to reach 0.25 μm

Silver plating bath preparation

-COVENTYA process SILVIUM 100

-20℃–0.5A/dm ²

Deposition time: 1 minute to 0.25 μm

Examples 9, 10 and 12 were prepared according to the invention and examples 7, 8 and 11 were prepared as references or for comparative reasons.

Table 2: has the following characteristics ofExamples of silver

Comparison of fig. 7, 8 and 9 concludes as follows: the indium layer has a barrier effect but is not as strong as the gold underlayer.

Fig. 10 demonstrates that the barrier effect can be improved by selecting a gold top layer.

Claims

1. A method of preparing an electroplated product by depositing a bottom layer, a diffusion barrier layer and a top layer on a surface of a substrate, the method comprising the steps of:

a) Depositing a bottom layer comprising or consisting of a first noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof, from a first electrolyte on a surface comprising or having a copper coating, said first electrolyte comprising at least one of said respective noble metal ion sources and at least one conductive salt,

b) Depositing a diffusion barrier layer on the bottom layer with an aqueous electroplating bath comprising at least one source of indium ions and at least one conductive salt, wherein the diffusion barrier layer prevents interdiffusion between the substrate and the top layer,

c) A top layer comprising or consisting of a second noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof is deposited on the diffusion barrier layer with a second electrolyte comprising at least one of the respective noble metal ion sources and at least one conductive salt.

2. A method for producing an electroplated product according to claim 1,

characterized in that the aqueous electroplating bath in step b) has a pH in the range of 1 to 14, preferably 2 to 11, still more preferably 4 to 10.

3. The method for producing an electroplated product according to claim 1 or 2,

characterized in that said at least one source of indium ions in said aqueous electroplating bath of step b) is selected from the group consisting of indium sulfate, indium chloride, indium acetate, indium sulfamate, and combinations or mixtures thereof.

4. The method for producing an electroplated product according to any one of the preceding claims,

characterized in that the concentration of the at least one indium ion source in the aqueous electroplating bath is preferably 0.1g/L to 20g/L, more preferably 0.2g/L to 15g/L, even more preferably 0.3g/L to 10g/L, and most preferably 0.5g/L to 10g/L.

5. The method for producing an electroplated product according to any one of the preceding claims,

characterized in that the sequence of steps a) to c) is not interrupted by a further deposition step, with the result that the layers deposited in steps a) to c) adjoin each other, preferably directly adjoin each other.

6. The method for producing an electroplated product according to any one of the preceding claims,

characterized in that at least one of said sources of noble metal ions in said electroplating bath of step a) is at least one source of Au ions, ag ions, and combinations thereof.

7. The method for producing an electroplated product according to any one of the preceding claims,

characterized in that at least one of said noble metal ion sources in said electroplating bath of step c) is selected from at least one ion source of Au, ag, pd, pt and combinations thereof, preferably at least one ion source of Au, ag and alloys thereof.

8. An electroplated product comprising a substrate comprising copper or having a copper coating, a bottom layer comprising or consisting of a noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof and a top layer comprising or consisting of a noble metal selected from Au, ag, pd, rh, ru, pt and alloys thereof deposited on said substrate,

characterized in that the bottom layer and the top layer are separated by a diffusion barrier layer comprising or consisting of indium or an alloy of indium and the top layer material, which diffusion barrier layer prevents interdiffusion between the bottom layer and the top layer.

9. The electroplated product according to claim 8,

characterized in that the diffusion barrier layer has a thickness of 1nm to 500nm, preferably 25nm to 300nm, still more preferably 50nm to 250 nm.

10. The electroplated product of claim 8 or 9,

characterized in that the underlayer has a thickness of 10nm to 500nm, preferably 25nm to 400nm, still more preferably 40nm to 300 nm.

11. Electroplated product according to one of the preceding claims, characterized in that the top layer has a thickness of 1nm to 500nm, preferably 3nm to 400nm, still more preferably 5nm to 300 nm.

12. Electroplated product according to one of the preceding claims, characterized in that the top layer comprises or consists of a noble metal selected from Au, ag, pd, pt and its alloys, preferably from Au, ag and their alloys.

13. Electroplated product according to one of the preceding claims, characterized in that the underlayer comprises or consists of gold or a gold alloy.